Solution Center for Nutrient Management
Solution Center for Nutrient Management
Solution Center for Nutrient Management
University of California
Solution Center for Nutrient Management

Nutrient Management Research Database

General Information

Research Title

Microbial responses and nitrous oxide emissions during wetting and drying of organically and conventionally managed soil under tomatoes

Research Specifications

Crop: Tomato
Soil Type: Yolo Silt Loam
County, State: Yolo, California
Year: 2005

Authors

Burger, M., Jackson, L.E., Lundquist, E.L., Louie, D.T., Miller, R.L, Rolston, D.E., Scow, K.M.

Summary/Abstract from Original Source

The types and amounts of carbon (C) and nitrogen (N) inputs, as well as irrigation management are likely to influence gaseous emissions and microbial ecology of agricultural soil. Carbon dioxide (CO2) and nitrous oxide (N2O) efflux, with and without acetylene inhibition, inorganic N, and microbial biomass C were measured after irrigation or simulated rainfall in two agricultural fields under tomatoes (Lycopersicon esculentum). The two fields, located in the California Central Valley, had either a history of high organic matter (OM) inputs (“organic” management) or one of low OM and inorganic fertilizer inputs (“conventional” management). In microcosms, where short term microbial responses to wetting and drying were studied, the highest CO2 efflux took place at about 60% water-filled pore space (WFPS). At this moisture level, phospholipid fatty acids (PLFA) indicative of microbial nutrient availability were elevated and a PLFA stress indicator was depressed, suggesting peakmicrobial activity. The highest N2O efflux in the organically managed soil (0.94 mg N2O-N m-2h-1) occurred after manure and legume cover crop incorporation, and in the conventionally managed soil (2.12 mg N2O-N m-2 h-1) after inorganic N fertilizer inputs. Elevated N2O emissions occurred at a WFPS >60% and lasted <2 days after wetting, probably because the top layer (0–150 mm) of this silt loam soil dried quickly. Therefore, in these cropping systems, irrigation management might control the duration of elevated N2O efflux, even when C and inorganic N availability are high, whereas inorganic N concentrations should be kept low during times when soil moisture cannot be controlled.

Research Highlights

Design and Methods

The research was conducted at the University of California Davis Long Term Research on Agricultural Systems project.
  • The organic system was a tomato-corn rotation with a winter legume cover crop of hairy vetch (Vicia villosa Roth), and Austian winter pea (Pisum sativum L.), as well as composted poultry manure additions and harvest residue inputs.
  • The conventional system recieved inorganic fertilizer (granular and banded) and harvest residue and employed a tomato-wheat rotation.
  • Both were furrow irrigated.
  • Soils were sampled during the tomato growing season when cropping systems were in their third year.
  • There were three 12x12m subplots in each of the 60x60 m plots per management type.
  • Soil gases were sampled 3 times throughout the growing season. At each sampling date, efflux of C02, total denitrification, estimated as efflux of N20 with acetylene inhibition, and N20 were measured 6, 30 and 54 h after the start of irrigation.
  • Gravimetric soil water content and inorganic N were determined daily, microbial biomass C and dissolved organic C were measured on the third day of each sampling period.
  • Microcosms were created using intact soil cores collected from random locations for measurement of CO2 and N20 efflux, soil moisture, inorganic N, Microbial biomass C (MBC), and Dissolved organic C (DOC) and Phospholipid Fatty Acids (PLFA) during simulated wetting and drying periods.

Results

Highlights of some important results are
  • For the organic system the 30 h N20 flux in April was highest of any sampling dates, while in the conventional system, the 30 h N20 flux in Octobor was highest.
  • In the organic system both C02 flux and DOC were greater than in the conventional system.
  • In both systems the highest MBC concentrations were measured in June, and the lowest in October.
  • C pools and C process rates and related measures were all greater in the organic system compared to the conventional system.
  • Mean total PLFA concentrations were greater in the organically compared to the conventionally managed soil.
  • N inputs, C availability and soil moisture all influenced N20 emissions. Microbial biomass C, total PLFA, respiration, C02 flux, and DOC were all higher in the organic than the conventional system.
  • Shifts in microbial populations occured after wetting in the organic treatment.
  • The data suggest that high inorganic N availability should be prevented during times when frequent rainfall is likely.

Additional Information

Related Research in Yolo County

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